1. Field of the Invention
The present invention relates to a projection-type display device and a light source control method therefor.
2. Description of the Related Art
There are known head-up display (HUD) apparatuses for vehicles for projecting projection light beams on a screen, which is a combiner disposed on a front glass of a vehicle or in the vicinity of the front of the front glass, so as to display an image (for example, refer to JP2013-246236A and JP2011-166396A). Through such an HUD, a user is able to see an image, which is displayed on the front glass or the like through projection light beams projected from the HUD, in a state where the image is superimposed on a landscape of the front of own vehicle on the rear side of the front glass or the like.
In general, for image display, the HUD is equipped with a light source that emits red light beams, a light source that emits green light beams, and a light source that emits blue light beams.
JP2013-246236A discloses a system using light sources such as semiconductor lasers, in which light emission efficiencies at a high temperature are greatly lowered, as light sources mounted on the HUD.
The HUD disclosed in JP2013-246236A has a display unit dedicated for notifying an abnormal state to a user. The HUD is configured to stop image display using the light sources under high temperature environment, in which a brightness of an image projected onto a screen is lowered, and to perform error display on the display unit.
JP2011-166396A discloses an HUD that performs image display by two-dimensionally scanning light beams emitted from light sources including a light source which emits red light beams, a light source which emits green light beams, and a light source which emits blue light beams, through scanning means. In the HUD, a brightness of important information, which should be notified to a user, is increased by controlling a speed of the scanning performed by the scanning means.